Is there a way to give a procedure access to it's argument list as a string?

Say I have something like:

var1=vector(1 2 "abc" 3 4)

var2=vector("x" "y" "z")

and I define a procedure like:

procedure( myProc(arg1 arg2])
  ...blah...)

and I call the procedure with 

myVar = myProc(var1 var2[1])

Is there any way to give the procedure access to the actual text of the arguments it was called with i.e. for the above example I'd like the procedure to be able to pick apart the string "arg1 arg2[1]". The reason I want to be able to do this is that I'd like the procedure to be able to peek into other elements of var2 even though it was only passed a specific element of it. Thanks!